Abstract

Introduction

Intervertebral disc tissue homeostasis is modulated by a variety of molecules. Silent
mating type information regulator 2 homolog 1 (SIRT1) plays a key role in various
physiological processes. The aim of the present study was to verify the expression
of SIRT1 and determine SIRT1 function in human intervertebral disc cell homeostasis.

Methods

Human nucleus pulposus (NP) cells were obtained from 24 surgical patients (mean age:
39.4 years) and monolayer-cultured. SIRT1 expression was investigated using RT-PCR
analysis and immunohistochemical staining. Quantitative real-time RT-PCR was performed
to detect mRNA expression of SIRT1 and other genes: aggrecan, collagen type 2 and Sox9. The effect of SIRT1 on the extracellular matrix metabolism of NP cells was examined
using recombinant human SIRT1 protein and a protein delivery reagent. Cell number
and proliferation activity were measured following SIRT1 treatment. To reveal the
deacetylation potential of transfected recombinant human SIRT1, western blotting for
acetylated p53 was utilized. R-phycoerythrin was used for the negative control.

Conclusions

We demonstrate for the first time that SIRT1 is expressed by human NP cells. SIRT1 expression was significantly elevated in an early degeneration stage. SIRT1 affected
both extracellular matrix metabolism and proliferation activity; the effect of SIRT1
was altered according to disease class and disc degeneration grade. SIRT1 appears
to play a key role in homeostasis during the human intervertebral disc degeneration
process.